03.08.2019 0:19, Max Reitz wrote: > On 02.08.19 20:58, Vladimir Sementsov-Ogievskiy wrote: >> hbitmap_reset is broken: it rounds up the requested region. It leads to >> the following bug, which is shown by fixed test: >> >> assume granularity = 2 >> set(0, 3) # count becomes 4 >> reset(0, 1) # count becomes 2 >> >> But user of the interface assume that virtual bit 1 should be still >> dirty, so hbitmap should report count to be 4! >> >> In other words, because of granularity, when we set one "virtual" bit, >> yes, we make all "virtual" bits in same chunk to be dirty. But this >> should not be so for reset. >> >> Fix this, aligning bound correctly. >> >> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> >> --- >> >> Hi all! >> >> Hmm, is it a bug or feature? :) >> I don't have a test for mirror yet, but I think that sync mirror may be >> broken >> because of this, as do_sync_target_write() seems to be using unaligned reset. > > Crap. > > > Yes, you’re right. This would fix it, and it wouldn’t fix it in the > worst way. > > But I don’t know whether this patch is the best way forward still. I > think call hbitmap_reset() with unaligned boundaries generally calls for > trouble, as John has laid out. If mirror’s do_sync_target_write() is > the only offender right now,
Another thing is migration/block. Should we care of it, is it supported at all? -- Best regards, Vladimir
